Model for the coexistence of d-wave superconducting and charge-density-wave order parameters in high-temperature cuprate superconductors

摘要

A theory describing a phase, where d-wave superconductivity coexists with charge-density waves (CDWs), has been developed. Numerical calculations were carried out for a specific case of cuprates when the CDW gap emerges at the nested antinodal regions of the two-dimensional Fermi surface. Different symmetries of the order parameters leads to their involved interplay so that the CDW one ∑(T) is predicted to become temperature re-entrant for certain ranges of model parameters. Here, T is the temperature. At the same time, the superconducting energy gap △(T) deviates substantially from the canonical d_(x~2-y~2) form. The CDW influence on △(T) is different from that on the critical temperature T_c. Hence, the resulting values of 2△(0)/T_c are shown to fall into the range 5÷8, which is well known for high-T_c oxides and has not been explained yet.